Sound reproducer and optical system therefor



INVENTOR ATTORNEY Oct. 29, M35. J. A. MAURER. m

SOUND REPRODUCER AND OPTICAL SYSTEM THEREFOR Filed March 17, 1931 Patented Oct. 29, 1935 SOUND In. H DUCER AND OPTICAL SYSTEM THEREFOR John A. Mower, In, New York, N. Y., assignor to Radio corporation oi America, a corporation of Delaware Application Mai-on 11, 1931, serial No. 523,284 3 Claims. (01. 119400.31)

Sound reproducers and recorders oi the soundaccurately defining the length or the linear light on-film type ordinarily comprise an optical sysimage thereon. tem which serves to form a linear image of a light My invention and the objects thereof will be source on the film sound record at an operational better understood from the following description photo-electric cell in the case 01 a sound reproin the appended claims. ducer. Such optical systems have heretofore been Figure 1 is a longitudinal section 01' my Optical complicated and extensive and particularly have system showing the lens mounted therein and its been extremely diiiicult to adjust and maintain relation to a film sound record. m

i; Figure 2 is an exploded view of the lens mount. isadvantage of many such systems Figure 3 is an end view of the lens mount. My

image on the film has been that the relative aperlindrical lens as hereinafter more fully described 35 intensity or slit width at the entrance end of the on nsin system or the equivalent thereof such optical system was necessarily kept undesirably as are standard commercial practice 01' such, for

large with attendant disadvantages as to sound p as is Shown n Eldred P nt 1, 11- 20 quality, heating of the apparatus and so forth. n the d 3 0 e tub l i Out a recess indie present invention relates to an improve- Cated at -4 n h r w n and whi h is 01 a ing therefor whereby applicant produces a cheapnor more than about 20 or 25% larger than such relatively inexpensive nd t th same t re1a a further recess 5 is cut extending the remainder 5 Another object of this i v ti is t produce only the aperture of the lens while the recess 4 in Another object of this invention is to provide This recess is made of a width of approxia th of focusing an optical system with great mately one-third that of the recess 4-3 and may facility and accuracy be within the same limits of tolerance although 40 Another object of this invention is to provide shghtrly less wlerance 1S preferable: a lens mount which will permit of the application As.wm be apparept from the drawing the of such method of focusing lindrical lens 2, which may be merely a section Another object of this invention is to provide of g-lass rqd s-elected so as to be freq from Impers rin metal and held fir a a i: th 3 1 manufacturing tolerances. fi vi by Screws g ms 6 end 0 m Another object of this invention is to provide a It will be apparent t lens mount w e the lens may be accurately metal allows for considerable variation in the di This entire assembly may be mounted in any usual manner which will hold the recesses l and 5 in proper transverse alignment with the film 8 and permit the movement of the tube toward or away from such film, or the mount may be such as to permit even rotational movement of the tube, such lateral alignment being accomplished independently.

It will be apparent that the edges of the members 6 and I accurately define the longitudinal limits of the linear image impressed on the film as rather clearly shown in Fig. 3 and thereby serve the additional function of a masking means.

The reason I make the recess 5 approximately one-third the diameter of the cylindrical lens 2 is because I find that at this dimension the bestmean between large relative aperture of the lens and accurate correction thereof is attained, and I preferably make this slot of a width of .04 inch while the rod is preferably of a diameter of .12

inch.

I further find that if the actual or virtual distance-of the source from which this lens receives its light is great relative to the focal length of this cylindrical lens, a linear image will be formed at a distance corresponding to the focal length of the lens for an object at infinity distance, or at least at a sufilclently close approximation thereto to permit this cylindrical lens to be focused substantially for infinity without undue error.

I further find that this focal length measured fourths of the diameter of the lens or in other words at a distance from the surface of the lens of one-fourth of its diameter.

I accordingly have devised a new and simple means for accurately focusing this optical system to wit:

I locate the cylindrical lens at a distance of one-fourth of its diameter from the film or from record surface 9 by placing a feeler-gauge between such surfaces and moving the lens or film carrier until these two surfaces are in contact with the thereon and serving as a mask therefor.

feeler-gauge. For example, with the lens referred to above, the distance thereof from the film will be .03 inch and by inserting a feeler-gauge of this thickness against the film in Fig. 1 and moving the tube forward until the surface of the lens 2 l exposed between the plates 6 and 1 contacts with such feeler-gauge, the lens is accurately focused on the film.

The usual variations in diameter of the lens will produce a relatively smaller variation in the 10 focal distance thereof but in case I desire to focus the lens with an extreme degree of accuracy I can determine the diameter of the particular lens to be focused by means of a micrometer or equivalent device and then choose a feeler-gauge hav- 1:; ing the total thickness amounting to one-fourth of the indicated diameter.

By the term photophonographic in the claims hereinafter included I refer to apparatus of that type which uses either a photographic method of ,0 recording or its equivalent or a photo-electric method of reproduction or its equivalent.

Having now described my invention, its operation and the method of adjustment thereof, I claim:

1. A lens system for photophonographic apparatus comprising an objective lens in the form of a complete cylinder and fixed means in cooperative relation therewith limiting the aperture thereof to one-third of the diameter of the lens. 30

2. A lens mount for a cylindrical lens'comprising a rectangular recess adapted to receive said cylindrical lens and a spring pressure member attached to said mounting, for retaining the lens 3. A lens mount for a cylindrical lens comprising a rectangular recess adapted to receive said cylindrical lens and a plurality of spring pressure members attached to said mounting, for retaining the lens thereon and providing masks 4 therefor.

JOHN A. MAURER, JR. 

